This invention relates to conveyors, and more particularly to an endless belt conveyor having a frame, a pair of spindles and an endless conveyor belt.
Known construction of an endless belt conveyor typically includes a frame assembly, a pair of head plates located at each end of the frame assembly, a spindle extending between each pair of head plates, and a conveyor belt engaged with the spindles. One of the spindles is drivingly interconnected with a motor, for rotating the spindle thereby to impart movement to the endless conveyor belt. The head plates are movably mounted to the frame assembly so as to provide selective adjustment of the position of the spindles, for providing proper belt tensioning and tracking. One such construction is illustrated in Domer et al U.S. Pat. No. 5,174,435, the disclosure of which is hereby incorporated by reference.
In the Domer et al ""435 patent, the conveyor frame is a ladder-type construction consisting of a pair of side frame members interconnected together via a series of transversely extending cross members, each of which is connected at its ends to the side frame members. T-shaped slots are formed in the side frame members, and each head plate is movably mounted to one of the side frame members by means of a T-nut slidably received within the T-shaped slot. A rack and pinion subassembly is mounted adjacent each end of the frame assembly, for selectively moving the head plates outwardly and inwardly relative to the frame assembly, and the T-nuts are employed to secure the head plates in position when proper belt tensioning is attained. A cam-type tracking mechanism provides adjustability in the angle of the spindle for providing proper belt tracking.
While this construction has been found to be highly satisfactory for both manufacturing and operational purposes, it involves certain drawbacks in overall part count and in assembly, in that the ladder-type frame construction is essentially a different subassembly for each available length of the conveyor frame assembly. Further, the belt tensioning and tracking components are separate subassemblies which require numerous parts and several assembly steps.
It is an object of the present invention to provide an endless belt conveyor construction which replaces the prior art ladder-type frame construction with a modular box-type frame construction, which lends itself to a reduced number of parts required for manufacturing conveyors of various lengths and which simplifies overall construction of the conveyor. It is a further object of the invention to provide a conveyor frame construction in which common components can be employed to manufacture conveyors of varying lengths in a relatively simple assembly process. It is a further object of the invention to provide such a conveyor construction in which the various components can be incorporated in a low profile arrangement without sacrificing strength of the conveyor frame and while maintaining optimal belt tensioning and tracking capabilities. A still further object of the invention is to provide such a conveyor construction which does not require a separate subassembly for rack and pinion type belt tensioning. Yet another object of the invention is to provide such a conveyor construction having a spindle mounting arrangement which facilitates mounting of the spindle to a bearing assembly which provides rotatable mounting of the spindle to and between the head plates. A still further object of the invention is to provide such a conveyor construction which is relatively simple in its components and assembly, which provides highly satisfactory frame strength, adjustability and operation.
In accordance with the invention, an endless belt conveyor includes a frame assembly having a pair of spaced apart side frame members. A bed plate spans between and is interconnected with the side frame members, for supporting the conveyor belt. In one form, the side frame members are separate from each other and are interconnected opposite the bed plate via a bottom plate interconnected with the side frame members in a manner similar to connection of the bed plate with the side frame members. In another form, the side frame members are formed integrally with a bottom wall spaced below the bed plate and extending between the side frame members.
Each side frame member includes axially extending slot-type engagement structure formed substantially throughout the entire length of the side frame member. The bed plate is formed to overlie an upwardly facing engagement area of each side frame member, and spaced openings are formed in the side portions of the bed plate. The openings are located so as to be in alignment with the slot-type engagement structure, and a connector fastener is adapted to pass through each opening and into engagement with the slot-type engagement structure for mounting the bed plate to the side frame members. The connectors or fasteners are preferably in the form of self-tapping screws, and the slot-type engagement structure is configured so as to provide threaded engagement of the self-tapping screws upon advancement of the screws into the slot-type engagement structure. The slot-type engagement structure is capable of receiving a connector or fastener at any point along its length, such that common side frame members can be employed for any length of the conveyor frame assembly simply by cutting the side frame member to an appropriate length.
For a conveyor frame in which the side frame members are separate from each other, the bottom plate is interconnected with the side frame members in the same manner as connection of the bed plate to the side frame members. In addition, an intermediate rail member is located between the side frame members and engaged with the bed plate and the bottom plate, to impart strength and rigidity to the frame assembly. The intermediate rail member includes top and bottom engagement sections, each of which includes slot-type engagement structure throughout its length. Again, openings are formed in the bed plate and the bottom plate in alignment with the slot-type engagement structure, and connectors or fasteners extend through the openings into engagement with the slot-type engagement structure for securing the bed plate and the bottom plate to the intermediate rail member. The intermediate rail member is cut to length according to the desired length of the conveyor assembly.
Each side. frame member includes an axially extending passage within which a gear rack is received and each gear rack is operatively engaged with one of the head plates. A pinion is rotatably mounted to and extends between the side frame members, and is engaged with the gear rack through an opening formed in the side frame member in communication with the passage within the gear rack is received. Rotation of the pinion results in extension or retraction of the gear racks, for extending and retracting the head plate members in unison so as to adjust the position of the spindle mounted to the head plates and thereby to control the tension in the conveyor belt. The pinion is engaged with a pair of bearings which are trapped between the bed plate and either the bottom plate or the bottom wall, to provide rotatable mounting of the pinion to the frame assembly. At least one end of the pinion is provided with engagement structure such as an irregular opening, and the pinion and is in alignment with an opening formed in a wall of the side frame member for providing engagement of a tool within the irregular opening, to enable a user to rotate the pinion to adjust belt tension. Each head plate is movably mounted to one of the side frame members via a selective locking arrangement, such as a T-slot and retainer arrangement, to enable the head plates to be secured in position relative to the frame assembly when the desired belt tension is attained. In a preferred form, the passage structure extends throughout the entire length of the side frame member. The opening, through which the spindle engages the gear rack, is formed in each side frame member after the side frame member has been cut to length. In this manner, common side frame components can be employed for conveyors of varying lengths, simply by cutting the side frame members to length and forming openings in the side frame members at desired locations toward one of the ends of the side frame members.
Belt tracking is preferably provided by forming a rib on the inside surface of the belt, which is received within a groove formed in the bed plate. Each spindle is mounted to a pair of the head plates using a spherical bearing assembly, which provides self-alignment of the spindle relative to the head plates to ensure belt tracking. Each spindle includes a shaft portion located within an aperture defined by inner wall structure associated with the bearing assembly. A passage is formed in the shaft portion, extending along an axis which is non-perpendicular to a longitudinal axis along which the shaft portion extends. An engagement member is received within the passage, and is operable to frictionally engage the shaft portion with the inner wall of the bearing assembly so as to mount the spindle to the bearing assembly. In one form, the passage extends inwardly from an end section of the shaft portion, in a direction substantially parallel to the longitudinal axis of the shaft portion. The end section of the shaft portion is radially expandable, and the engagement member includes a tapered head section which causes radial expansion of the end section upon advancement of the engagement member within the passage. In another form, the passage is oriented at an acute angle relative to the longitudinal axis of the shaft portion, and opens onto oppositely facing surfaces defined by the shaft portion. An entrance to the passage is located outwardly of the bearing assembly, and the engagement member is advance from the entrance through the passage and outwardly of the passage opposite the entrance, into engagement with the inner wall of the bearing, so as to frictionally engage the shaft portion with the inner wall of the bearing.
The various features of the invention can be separately incorporated into a conveyor construction, and each provides certain advantages, such as reduction in the number of components, strength of the conveyor frame, or ease of manufacture, assembly and operation. In a particularly preferred form, the features are employed in combination to provide a conveyor construction which involves significant improvements in components, assembly and operation.
Various other features, objects and advantages of the invention will be made apparent from the following description taken together with the drawings.